1. Technical Field
The present invention relates to the domain of realisation of trim elements or elements of inner lining of automobile vehicles, in particular elements of this type comprising or constituted by a sheet or plate of thermoplastic material, formed in adapted manner and optionally presenting a raised pattern formed in the mass.
More specifically, the object of the invention is a mold device for the manufacturing by molding under negative pressure of pieces, starting from the sheets or the plates, and a manufacturing process using this device.
2. Related Art
Various processes for the manufacturing of pieces by molding under negative pressure (better known under the English name “Negative Vacuum Forming”) are already known in the state of the art (see, for example: FR 2 900 862, US 2013/0221698).
Generally, in this type of process, a sheet or a plate of plastic material is preheated and then placed between two parts of the mold (or half molds) which preforms it during the closure and, after the complete closure of the mold, relative vacuum is applied at the level of the part of the mold that comes into contact with the visible face of the piece in order to realise the definitive molding of the piece. Eventually, during the application of pressure, due to the surface aspiration, a raised pattern or graining is realised on the visible surface (negative pattern that is present on the part of the mold subjected to suction).
This method of molding by vacuum has many advantages among which, in particular, is the excellent quality of the pattern and the deformations that the visible surface must have, as well as their precise localisation.
Nonetheless, when the pattern has to be changed, even locally, and/or if one or several particular deformations have been foreseen, for example, for different versions of the same piece, it is necessary to have the same number of mold parts (at least for the visible face) as the versions of the piece, even if certain of these versions distinguish themselves from each other only by minor or local differences (modification of the height or the form of a given reinforcement of the accommodation of a given accessory, management of the presence/absence of locally deformed zones, creation of drafts of the mounting or anchoring zones of the equipment or the salient decorative elements, . . . )
In addition, the necessary replacement of the parts of the mold between two phases of the manufacturing of different versions of the same piece leads to a fall in the efficiency and productivity of the equipment and the personnel and requires the acquisition of specific means permitting to make a rapid change in the parts of the mold.